Welcome to ST055 Engine Electronics!

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Welcome to ST055 Engine Electronics!
meeknet.co.uk/e64
Welcome to ST055 Engine Electronics!
ST055 Engine Electronics is 5 days in length.
This handout is representative of selected 4, 6, 8, and 12 cylinder Engine Management
Systems from 1996 to present. The handout serves two purposes; Instructor lead training
and “stand alone” system reference material for the BMW Technician.
Obviously, all of the material in the handout can not be covered in 5 days, therefore a system will be selected to cover the basic required information. The information from other systems will cover the differences or variants that make them unique. Where possible, use the
latest diagnostic equipment and DISplus/MoDIC software programs.
Objectives
The Instructor will familiarize the BMW Technicians with an understanding of the current
Engine Electronics Systems and diagnostic skills. Also the Technicians will perform hands
on practicals in the shop to ensure participation in diagnosis and component testing.
Objectives are provided on page 2 of each system to guide you to the key learning points
of each module. Review questions are provided at the conclusion of each module to verify
that you achieve the learning objectives during the course. A final test will be given at the
end of the course.
It is very important to study the content which will assist you with important “on
the job” information and successful completion of this course.
As a Mention . . .
Please visit our website at Http://www.bmwtis.net for the latest information about:
• Service Information
Bulletins
• Technical Training Information
Courses
• Repair Information
Manuals
• Electrical Troubleshooting Manual Information
Wiring Schematics
• Technician Feedback Systems
Quality Control Information Reports
The chart shown below is a quick reference of BMW Engine Management Systems by
application to BMW models, engines and model years. This will help you to get familiar with
the systems by identifying the correct version that you are diagnosing.
Engine Management Control Versions
VERSIONS
MODEL
ENGINE
MODEL YEAR
M1.2
E32 / M5
M70 / S38
M70 = 1988 - 1999
S38 = 1991 - 1993
M1.7
E31 / E32
M70
1991 - 1994
M1.7
E30
M42
1990 - 1993
M1.7
E36
M42
1992
M1.7
E36
M42 / DISA
1992 - 1995
M1.7.1
E31
* M1.7.2
E36
M42 / DISA
1995
M3.1
E34
M50
1991 - 1992
M3.1
E36
M50
M3.3
E32
M60
1993 - 1994
M3.3
E31 / E34
M60
1994 - 1995
M3.3.1
E34 / E36
M50 TU
1993 - 1995
M5.2
E36 / Z3
M44
1996 - 1998
E31 / E38 / E39
M62 / M73
1995 - 1997
* MS41.1
E36 / E39 / Z3
M52
1996 - 1998
* MS41.2
E36 M3
S52
1996 - 1998
Bosch = M
Siemens = MS
M5.2
* M5.2.1
E38 / E39
S70
M62 / M73
1994 - 1995
1992
> 1998
* MS42
E46 / E39 / Z3
M52TU
* MS43
E46 / E39 / E53 / Z3
M54
> 2001
* ME 7.2
E39 / E38 / E53
M62TU
> 1999
* MS S52
E39 (M5) E52 (Z8)
S62
>1999
* MS S54
E46 (M3)
S54
> 2001
* = Systems covered in this course
1998 - 2000
Table of Contents
Subject
Page
M1.7.2 . . . . . . . . . . . . . . .
Objectives of the Module
Purpose of the System . .
System Components . . .
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Power Supply . . . . . .
Principle of Operation
Workshop Hints . . . .
Tools and Equipment
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Air Management . . . .
Principle of Operation
Workshop Hints . . . .
Tools and Equipment
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. . . . . . . . . . . . . . . . . . . .16
. . . . . . . . . . . . . . . . . . . .21
Fuel Management . . .
Principle of Operation
Workshop Hints . . . .
Tools and Equipment
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. . . . . . . . . . . . . . . . . . . .44
Ignition Management
Principle of Operation
Workshop Hints . . . .
Tools and Equipment
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.5
.6
.7
.8
Emissions Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65
Evaporative Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65
Exhaust Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
Principle of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71
Workshop Hints. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Tools and Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Performance Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .78
Variant Coding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83
Workshop Hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .84
Tools and Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Review Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
M1.7.2
Model: E36-M42 Engine
Production Date: 1995
Manufacturer: Bosch
Pin Connector: 88 Pins
Objective of the Module
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Objectives of the Module
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• kjkfsrdouijoekfjsdflkjeiowutoidsutiglhndkjhfdiouyhtiorueoigjlj
•After
jckjfkdiojdslkjfvjcxkgkfhdgvhjchbkjhfkjgvhbkhcjvhdufhgkuchvj
completing this module, you will be able to:
• hfdjfhksdfjkhdsjfhsjdhfjdshjfhsdjfhkdjhfdjfhdjfhjhdfiuyeruetyutyuryturtyurytuirytuiyruityyt
•• Describe
hfjghejytiufdhkdhfjshdjfhdjhfjdhfjdhfjdhfoeuriewuooweiurieuiuiuiuiuiuiuiuiuiuoiewuro
the Power Supply for the Fuel Injectors
• jhjdjfhidushfiryiusdhfkjdshfkjhdsjfhsdjhfkjshdfdskjfhdsjfhjdhjfhdjhfjdhfjdhkjsytiu
• jnhfkjhgkrjtikgfjdlgjlfkglfglfgfjkjjfgjjjhjrytuyreuuyueyuyuy
• Name the Components of the Fuel Supply System
• List the Inputs Required for Ignition Operation
• Decribe the Knock Sensor Function
• Name Two Types of Emissions the ECM Controls
• List Two Reasons for the “CHECK ENGINE” Light to Illuminate
• Describe Semi-Sequential Fuel Injection
• Understand How EWS Affects ECM Output Functions to Deter Vehicle Theft
2
ST055 M1.7.2
M1.7.2
Purpose of the System
The M1.7.2 system manages the following functions:
Air:
Fuel:
Ignition:
•
•
•
•
• Fuel Supply
• Fuel Injection
• Direct Ignition
• Knock Control
• Primary Ignition Monitoring
Idle Speed Valve
Throttle Position
Air Flow Meter
DISA
DME
M1.7.2
Emissions:
Performance Controls:
•
•
•
•
•
• Output of Injection Signal (Ti) for MPG Gage
• Interaction with EGS (ignition timing inter
vention)
• Throttle position (DKV) for EGS
• Output of Engine RPM for Tachometer
• A/C Compressor Control
• EWS I and EWS II
Lambda Adaptation
Oxygen Sensor Heating
Primary Ignition Monitoring
Evaporator Purge Valve Control
CHECK ENGINE Light
3
ST055 M1.7.2
System Components: INPUTS - PROCESSING - OUTPUTS
12550012.eps
4
ST055 M1.7.2
Power Supply
12550011.eps
KL30 - Battery Voltage: It supplies the operating voltage to the ECM. Battery voltage also
sustains system memory for fault codes and adaptation values.
KL15 - Ignition Switch: When the ignition is switched “on” the ECM is informed that the
engine is about to be started. KL15 also supplies voltage to the Engine Control Module
Relay. Switching KL15 “off” removes the ECM operating voltage.
Engine Control Module Relay: It provides the operating voltage for:
• ECM
• Fuel Pump Relay
• Fuel Injectors
• Oxygen Sensor Heating
• Idle Speed Valve
• Purge Valve
• Intake Air Resonance Changeover Valve
• EGS “wakeup” Call (Terminal 87a)
Ground: Multiple ground paths are necessary to complete current flow through the ECM.
The ECM ground pin numbers and functions are:
Pin#
Ground
06
Fuel Injection
28
34
Electronics and Sensor Shielding
Remaining Output Stages (Except Ignition & Injection)
43
55
Sensors
Ignition
71
Oxygen Sensor Signal
5
ST055 M1.7..2 Power Supply
Principle of Operation
Battery Voltage is monitored by the ECM for fluctuations. It will adjust the output functions to compensate for a lower (11.7v) and higher (14v) voltage value. For example, the
ECM will:
• Modify Pulse Width Duration of Fuel Injection
• Modify Dwell Time of Ignition
When KL15 is switched “on” the ECM is ready for engine management. The ECM will activate ground to energize the Engine Control Module Relay. The Engine Control Module
Relay supplies operating voltage to the ECM and the previously mentioned operating components.
When KL15 is switched “off” the ECM operating voltage is removed. The ECM will maintain a ground to the Engine Control Module Relay for a few seconds to hold the Evaporative
Purge Valve closed (to prevent engine run on).
Ground is required to complete the current
path through the ECM. The ECM also:
• Internally links a constant ground (1) to the
engine sensors.
• Switches ground (2) to activate components
12550006.eps
6
ST055 M1.7.2 Power Supply
Workshop Hints
Power Supply - Testing
Inadequate power and ground supply can result
in:
K6300 Engine Control Module Relay
• No Start
• Hard Starting (Long Crank Times)
• Inaccurate Diagnostic Status or ECM
Not Found
• Intermittant/Constant Check Engine Light
• Intermittant/Constant Driveability
Problems
Power supply including fuses should be tested
for:
12550007.eps
• Visual (1) Blown Fuse
• Available Voltage 2
• Voltage Drop (Dynamic Resistance) (2)
• Resistance of Cables and Wires (2)
The ignition (KL15) must be switched
off when removing or installing the
ECM connector to prevent voltage
spikes (arcing) that can damage the
Control Module!
12550006.bmp
The Engine Control Module Relay (located in the
fuse box) should be tested for:
• Battery Voltage and Switch Ground (1)
• Resistance (1)
• Battery Voltage and Voltage Drop (2)
12550008.eps
7
ST055 M1.7.2 Power Supply
Tools and Equipment
Power Supply
When testing power supply to an ECM, the
DIS/MoDIC multimeter function as well as a reputable hand held multimeter can be used.
88 Pin
Adapter
It is best to make the checks at the ECM connection, this method includes testing the wiring
harness.
The correct Universal Adapter for the M1.7.2
application should be used (#88 88 6 614 410).
This will ensure the pin connectors and the harness will not be damaged.
12550005.eps
The interior of this Universal Adapter is shielded,
therefore it is vital that the ground cable is connected to the vehicle chassis whenever the
adapter is used.
The adapter uses a Printed Circuit board inside
keeping the capacitive and inductive load to a
minimum.
12550007.bmp
When installing the Universal Adapter to the
ECM (located below the windshield on the passenger side of the engine compartment), make
sure the ignition is switched off.
The Engine Control Module Relay should be
tested using the relay test kit (P/N 88 88 6 613
010) shown on the right.
This kit allows testing of relays from a remote
position.
Always consult the ETM for proper relay connections.
8
ST055 M1.7.2 Power Supply
12550001.bmp
Air Management
12550013.eps
Throttle Valve: The mechanical throttle valve
regulates the intake air flow and it is linked by a
cable to the accelerator pedal.
The throttle valve is a two stage (progressive
linkage) plate arrangement with integral closing
springs. This allows a smaller primary opening
(1) for low to mid-range rpm and a larger secondary opening (2) that opens for the higher
rpm range.
The throttle valve is heated by engine coolant to
prevent condensation from “icing”. The throttle
valve is “preset” and should not be adjusted.
Throttle Position Sensor: A potentiometer is
mounted on the throttle housing which provides
the ECM with a voltage value (0-5v) that represents throttle angle position and rate of movement. The sensor receives its power supply
from the ECM.
The Potentiometer is non-adjustable because
the ECM “learns” the throttle angle voltage at
idle speed. If the throttle position sensor is
replaced, the ECM must be disconnected from
the power supply for at least one minute (to
clear memory).
13550000.jpg
M1.7.2
Control
Module
43 12 59
13550002.eps
9
ST055 M1.7.2 Air Management
Idle Speed Control Valve: This is a two wire
control valve that regulates air by-passing the
throttle valve to control the engine idle speed.
The idle speed control valve is spring loaded
closed. It will “failsafe” to a fixed opening (21%)
to allow the engine to idle in the event of a
power failure.
The valve is supplied with battery voltage from
the Engine Control Module Relay. The valve
opening is controlled by the ECM modulating
the ground signal which opens the valve against
spring tension.
13550001.eps
Air Flow Volume Sensor: This sensor measures the
total volume of air drawn into the engine.
The ECM provides the power supply for the Air Flow
Volume Sensor. A potentiometer is connected to the
sensing flap and as air flow causes the sensing flap to
move, a varying voltage signal (0-5v) is sent to the
ECM that “represents” the inducted air volume.
59
14
41
Attached to the sensing flap is a “compensation flap”
that moves within a closed chamber. This creates a
dampening effect on flap movement for pulsations in
the intake system caused by cylinder filling and intake
valve operation.
12550013.eps
NOTE: The Air Flow Volume Sensor is non-adjustable.
10
ST055 M1.7.2 Air Management
Air Temperature Signal: The Air Flow Volume Sensor
contains an integral air temperature sensor. This signal
is needed by the ECM to correct the air volume input
for changes in the intake air temperature (air density).
The sensor is located in front of the measuring flap.
The ECM provides the power supply to this component. The sensor decreases in resistance as the temperature rises and vice versa (NTC). The ECM monitors
an applied voltage to the sensor (5v) that will vary as air
temperature changes the resistance value (0-5v).
13550001.jpg
Differential Air Intake System (DISA): DISA
allows the dynamics of varied intake manifold
tuning. This feature provides necessary intake
air “velocity” producing good mid-range torque.
Additionally, DISA can divert intake air flow providing “volume” for higher rpm requirements.
The ECM closes the changeover valve to take
advantage of a long single intake runner at midrange RPM. This produces air velocity that
increases engine torque at mid-range.
13550003.jpg
At high rpm, the ECM opens the changeover
valve allowing the engine breathing dynamics
to change to the dual short air pipes (volume).
This change enables additional power output at
the higher RPM range.
13550004.jpg
11
ST055 M1.7.2 Air Management
To accomplish this function, the M42 intake
manifold incorporates a non-replaceable brass
change over valve.
The DISA system vacuum components are:
• Motor (actuator)
• Reservoir
• Solenoid
• Check Valve
The solenoid receives voltage from the Engine
Control Module Relay and the ECM controls the
ground supply to activate the solenoid.
13550005.jpg
Pressure Control Valve: The pressure control
valve varies the vacuum applied to the
crankcase ventilation depending on engine
load. The valve is balanced between spring
pressure and the amount of manifold vacuum.
The oil vapors exit the separator labyrinth in the
cylinder head cover (1). The oil vapors are
drawn into the intake manifold (3) regulated by
the pressure control valve (2).
At idle when the intake manifold vacuum is high,
the vacuum decrease the valve opening and
only allows a small amount of crankcase vapors
to be drawn into the intake manifold.
11550046.bmp
At part to full load conditions when intake manifold vacuum is lower, the spring opens the
valve and additional crankcase vapors are
drawn into the intake manifold.
11550001.jpg
12
ST055 M1.7.2 Air Management
Principle of Operation
Air flow into the engine is regulated by the Throttle Valve or the Idle Speed Control Valve.
Both of these air “passages” are necessary for smooth engine operation from idle to full
load. On the M1.7.2 system, the Throttle Valve is mechanically controlled and the Idle
Speed Control Valve is electrically controlled. All of the ECM monitoring, processing and
output functions are a result of regulated air flow.
12550013.eps
The Throttle Position Sensor is monitored by the ECM for throttle angle position and rate
of movement. As the throttle plate is opened, a rising voltage signal (up to 5v) requests
acceleration and at what rate. The ECM will increase the volume of fuel injected into the
engine, advance the ignition timing and decrease the Idle Speed Valve opening (air is now
going by the throttle plate). The “full throttle” position indicates maximum acceleration to
the ECM, this will have an effect on the A/C compressor (covered in Performance Controls).
As the throttle plate is closed (integral springs), a decrease in voltage signals the ECM to
activate fuel shut off if the rpm is above idle speed (coasting). The Idle Speed Control Valve
will then be opened to maintain idle speed.
The ECM monitors the engine idle speed in addition the Throttle Position Sensor voltage.
The voltage value is “learned” at the correct idle speed and if the voltage value has changed
(mechanical wear of throttle plate or linkage), the ECM will adjust the Idle Speed Control
Valve to maintain the correct idle speed based on the “new” voltage. To clear this “learned”
value, disconnect the ECM for at least one minute. If the Throttle Position input is defective, a fault code will be set and the “CHECK ENGINE” Light will illuminate. The ECM will
maintain engine operation based on the Air Flow Volume Sensor and the Engine RPM
Sensor.
The Idle Speed Control Valve is controlled by the ECM modulating the ground signal to
the valve, opening it against spring pressure. By varying the duty cycle applied to the winding, the valve can be progressively opened, or held steady to maintain the idle speed. If the
Idle Speed Control Valve circuit is defective, a fault code will be set and the “CHECK
ENGINE” Light will illuminate. The valve will spring to the fixed opening, allowing the engine
to idle.
13
ST055 M1.7.2 Air Management
There are additional factors that influence the ECM in regulating idle speed:
• The RPM sensor input allows the ECM to
monitor engine speed because of loads that
cause idle fluctuations due to drag on the
engine: power steering, thick oil (fractional
forces), etc.
• Cold engine temperature (coolant NTC) provides
higher idle speed to raise temperature sooner.
• Vehicle speed informs ECM when the vehicle
is stationary and requires idle maintenance
• A/C on request from the climate control system
(arming the ECM) and compressor engage
(stabilize idle speed) acknowlegment.
• Range selector provides a Park/Neutral input to
the ECM identifying when the vehicle is in a
drive gear. This signal allows idle stabilization
for the increased load on the engine.
Idle Speed
Control Valve
13550004.eps
The Air Flow Volume Sensor sends a varying voltage (0-5v) to the ECM representing the
measured amount of intake air volume. This input is used by the ECM to determine the
amount of fuel to be injected. If this input is defective, a fault code will be set and the
“CHECK ENGINE” Light will illuminate. The ECM will maintain engine operation based on
the Throttle Position Sensor and Engine RPM Sensor.
The Air Temperature Signal allows the ECM to make a calculation of air density. The varying voltage input from the NTC sensor indicates the larger proportion of oxygen found in
cold air, as compared to less oxygen found in warmer air. The ECM will adjust the amount
of injected fuel because the quality of combustion depends on oxygen sensing ratio.
The ignition timing is also affected by air temperature. If the intake air is hot the ECM retards
the base igniton timing to reduce the risk of detonation. If the intake air is cooler, the base
ignition timing will be advanced. If this input is defective, a fault code will be set and the
“CHECK ENGINE” Light will illuminate.
14
ST055 M1.7.2 Air Management
DISA is controlled by the ECM activating the Change Over Solenoid below 4,840 RPM.
• When activated the solenoid applies vacuum
to the change over valve and the valve closes,
providing the long pipe effect.
• Above the RPM, the solenoid is switched off
and the Change Over Valve springs opens,
providing the short pipe effect.
• On decel, the solenoid will not be activated
until 4,760 RPM. This over lap prevents
repeated opening and closing of the valve while
driving at a constant engine speed of 4800
rpm.
13550006.jpg
13550007.jpg
If there is a defect in this system, the Changeover Valve will be opened to ensure intake air
availability for maximum power (short pipe affect). The Vacuum Motor and valve shaft are
both spring loaded to open the Changeover Valve if vacuum is not applied.
15
ST055 M1.7.2 Air Management
Workshop Hints
Air Management
Unmetered air leaks can be misleading when diagnosing faults causing Check Engine
Light/driveability complaints. Refer to S.I. # 11 03 92 (3500) for testing intake vacuum
leaks.
Crankcase Ventilation System
A fault in this system can often “mislead” diagnosis. This type of fault can produce:
• Mixture/Misfire Defect Codes
• Whistling Noises
• Performance/Driveabiltity Complaints
Please refer to the following Service Information Bulletins for details on the Crankcase
Ventilation System:
• Crankcase Ventilation System Check S.I. #11 05 98
• Throttle Housing Recall Campaign (Crankcase Ventilation Routing) S.I. #13 06 91 (3440)
Throttle Valve and Throttle Position Sensor
These components are non-adjustable and tampering is not permitted. However, the
attaching throttle and cruise control cables should be adjusted (refer to Repair Instructions).
Please refer to the following Service Information Bulletins for details on the Throttle Valve
Housing and Throttle Position Sensor:
• Increase Pedal Effort S.I. #13 03 94 (4042)
• Throttle Body Recall Campaign (Throttle Body Heater) S.I. #13 02 94 (3980)
• Throttle Potentiometer - Fault code 12 S.I. #13 09 90 (3141)
16
ST055 M1.7.2 Air Management
Throttle Position Sensor - Testing
The Throttle Position Sensor (potetiometer) can
be tested with the following methods:
M1.7.2
Control
Module
• DIS Status Page (approx. 0.6v idle to 4.2v full
throttle.
• DIS Oscilloscope - Select from the Preset
Measurements which requires taking the
measurement with the ECM and Universal
Adapter connected to the circuit.
43
12
59
• Resistance check of the entire circuit, using
the Universal Adapter with the ECM
disconnected (approx. 1-4 K ohms).
13550005.eps
Idle Speed Control Valve - Testing
• The Idle Speed Control Valve and idle air circuit
(passage ways) should be checked for physical
obstructions.
• The resistance of the valve winding should be
checked (8 +/-2 ohms).
• The ECM output and Idle Speed Control Valve
operation can be tested by “Component
Activation” on the DIS/MoDIC.
• The Pulse Width Modulated ground output
from the ECM can be tested using the DIS/
MoDIC Oscilloscope.
• Consult Technical Data for specified idle speed.
13550008.jpg
13550002.eps
17
ST055 M1.7.2 Air Management
Air Flow Volume Sensor
This component is non-adjustable and tampering is not permitted.
A faulty Air Flow Volume Sensor can produce the following complaints:
•
•
•
•
Difficult To Restart When Engine Is Hot
Engine Starts Then Stalls
“CHECK ENGINE” Light Illuminated
Engine Starts And Runs Only With
Accelerator Pedal Depressed
Please refer to the following Service Information Bulletin for details on the Air Flow Volume
Sensor:
• Fault Code “41” S.I. #12 09 95
Some early versions have been modified with an
additional harness. This is a BMW approved
modification, refer to S.I. #13 03 91 (3290) for
details.
13550009.jpg
The Air Flow Volume Sensor should be checked
for:
• Code Number (1)
• Production Date (2)
13550010.jpg
18
ST055 M1.7.2 Air Management
Air Flow Volume Sensor - Testing
The Air Flow Volume Sensor (potentiometer) can be tested with
the following methods:
• DIS Status Page (Up/Uv Ratio
0.1 - 0.3 at idle speed).
• DIS Oscilloscope - Select from
the Preset Measurements which
requires taking the
measurements with the ECM
disconnected and the Universal
Adapter connected to the
circuit.
• Resistance check of the entire
circuit, using the Universal
Adapter with the ECM
disconnected.
13550004.eps
Air Temperature Signal Testing
NTC sensors decrease in resistance as the temperature rises and
vice versa. The ECM monitors the
sensor voltage which varies as
temperature changes the resistance value. For example, as temperature rises:
• Resistance through the sensor
decreases.
• Voltage drop across the sensor
decreases.
• Input signal voltage also
decreases (5-0v).
14
77
This Sensor should be tested
using:
• DIS/Modic Status page.
• DIS/Modic Multimeter
At 20º C 2.2 - 2.7 k ohms
13550005.eps
19
ST055 M1.7.2 Air Management
DISA - Testing
The DISA System can be tested by raising the RPM to 4,840 (briefly) and visually checking
the Vacuum Motor Actuator Arm for movement.
If the Actuator Arm does not move, repeat test and check for vacuum at:
• Vaccum Motor
• Solenoid Valve
• Reservoir
Repeat the test to verify the ECM is providing a ground signal to the Solenoid Valve.
.
18
13550011.jpg
20
ST055 M1.7.2 Air Management
Tools and Equipment
The DIS/Modic as well as a reputable hand held
multimeter can be used when testing inputs/
components.
It is best to make the checks at the ECM connection, this method includes testing the wiring
harness.
The correct Universal Adapter for the M1.7.2
application should be used (#88 88 6 614 410).
This will ensure the pin connectors and the harness will not be damaged.
07550003.eps
The interior of this Universal Adapter is shielded,
therefore it is vital that the ground cable is connected to the vehicle chassis whenever the
adapter is used.
88 Pin
Adapter
The adapter uses a Printed Circuit board inside
keeping the capacitive and inductive load to a
minimum.
12550010.eps
When installing the Universal Adapter to the
ECM (located below the windshield on the passenger side of the engine compartment), make
sure the ignition is switched off.
The Slack Tube Manometer Test Tool (#99 00 0
001 410) should be used to troubleshoot
crankcase ventilation valves.
12550002.jpg
21
ST055 M1.7.2 Air Management
Fuel Management
12550014.eps
Fuel Tank: The fuel tank is made of
high density polyethylene (reduced
weight) which is manufactured to
meet safety requirements.
Running Losses
3/2 Way Valve
Assembly
A “saddle” type tank is used which
provides a tunnel for the driveshaft but
creates two separate low spots in the
tank.
A Syphon jet is required with this type
of tank to transfer fuel from the left
side, linked to the fuel return line.
As fuel moves through the return, the
siphon jet creates a low pressure (suction) to pick up fuel from the left side
of the tank and transfer it to the right
side at the fuel pick up.
22
ST055 M1.7.2 Fuel Management
13550006.eps
Fuel Pump: The electric fuel pump supplies constant
fuel volume to the injection system. This system uses a
single submersible (in the fuel tank) pump. The inlet is
protected by a mesh screen.
When the fuel pump is powered, the armature will
rotate the impeller disk creating low pressure at the
inlet. The fuel will be drawn into the inlet and passed
through the fuel pump housing (around the armature).
The fuel lubricates and cools the internals of the pump
motor.
The fuel will exit through a non-return check valve to
supply the injection system. The non-return check
valve is opened by fuel exiting the pump and will close
when the pump is deactivated. This maintains a
“prime” of fuel in the filter, lines, hoses and fuel rail.
13550056.eps
The pump contains an internal overpressure relief valve
that will open (reducing roller cell pressure) if there is a
restriction in the fuel supply hardware.
Fuel Supply Hardware: The fuel is transfered from
the fuel pump to the fuel filter then on to the fuel rail.
This is accomplished by a combination of steel lines (2)
and high pressure hoses (1).
The fuel pump delivers more volume than the injection
system requires. The unused fuel is routed through a
return line to the tank. The fuel is constantly circulated
in this manner.
13550012.bmp
The fuel filter “traps” contaminents before they reach
the fuel injectors and should be replaced at the specified interval. The arrow (on the filter) denotes the installation direction. The large filter size also serves as a
volume reservoir for pressurized fuel (dampening fuel
pump pulsations).
The fuel rail distributes an even supply of fuel to all of
the injectors, and also serves as a volume reservoir.
13550007.eps
23
ST055 M1.7.2 Fuel Management
Fuel Pressure Regulator: The Fuel Pressure Regulator maintains a constant “pressure differential" for
the fuel injectors.
The fuel pressure is set to 3.0 bar (+/- 0.2) by internal
spring tension on the restriction valve.
The vacuum chamber is sealed off by a diaphragm
which is connected by a hose to the intake manifold.
Intake manifold vacuum regulates the fuel pressure by
assisting to compress the spring (lowering fuel pressure).
When the restriction valve opens, unused fuel returns
back to the fuel tank.
13550025.jpg
Examples of “pressure differential” are:
• At low to part throttle, intake manifold vacuum is available at the tip of the fuel injectors
to enhance fuel “flow through”. Vacuum is also applied to the fuel pressure regulator
vacuum chamber, causing the diaphragm to compress the spring which opens the
restriction valve. This lowers the fuel pressure available to the fuel injectors.
13550008.eps
24
ST055 M1.7.2 Fuel Management
• Wide open throttle depletes intake manifold vacuum at the tip of the fuel injectors and in
the fuel pressure regulator vacuum chamber. The spring closes the restriction valve to
raise fuel pressure available to the fuel injectors. This maintains pressure differential (fuel
flow through) for the fuel injectors.
Spring
Closes Restriction Valve
(Raising Fuel Pressure)
3 Bar
Pressure
Regulator
Fuel Injector
Fuel
Return
To
Tank
Atmospheric Pressure
Throttle Valve
Intake Manifold
Intake Port
13550009.eps
By maintaining constant Fuel Pressure Differential through vacuum sensing (engine load),
the ECM can then regulate volume and mixture by the length of time the injectors are open
(duration).
The Fuel Pressure Regulator is mounted on the
fuel rail (arrow).
13550014.jpg
25
ST055 M1.7.2 Fuel Management
Bosch Fuel Injectors: The Fuel Injectors are electronically controlled solenoid valves that
provide precise metered and atomized fuel into the engine intake ports. The Fuel Injector
Valve consists of:
1.
Fuel Strainer
2.
3.
4.
5.
Electrical Connector
Solenoid Winding
Closing Spring
Solenoid Armature
6.
Needle Valve
7.
Pintle
Fuel is supplied from the fuel rail to the injector body.
The fuel is channeled through the injector body to the
needle valve and seat at the tip of the injector.
Without electrical current, the needle valve is sprung
closed against the seat.
The Fuel Injectors receive voltage from the Engine
Control Module Relay. The ECM activates current flow
through the injector solenoid creating a magnetic field
that pulls the needle “up” off of its seat.
The pressurized fuel flows through the opening and
deflects off of the pintle.
13550075.jpg
The pintle (tip of the needle) is a cone shaped deflector that “fans out” the fuel spray into an angled pattern
which helps to atomize the fuel.
When the ECM deactivates current flow, the needle
valve is sprung closed against the seat and fuel flow
through the injector is stopped.
The length of time that the ECM activates the Fuel
Injectors is very brief, the duration is in milli-seconds
(ms). This affects the mount of fuel volume flowing
through the Fuel Injectors.
The ECM will vary the length of time (ms) to regulate
the air/fuel ratio (mixture).
26
ST055 M1.7.2 Fuel Management
13550010.eps
The Fuel Injectors are mounted in rubber “orings” between the fuel rail and the intake manifold to insulate them from heat and vibration.
This insulation also reduces the injector noise
from being transmitted through the engine
compartment. The Fuel Injectors are held to the
fuel rail by securing clips (arrow).
If a Fuel Injector is faulty (mechanical or electrical), it can produce the following complaints:
13550016.jpg
• “CHECK ENGINE” Light
• Excessive Tailpipe Smoke (leaking)
• Engine Hydrolock (leaking)
• Misfire/Rough Idle (Leaking or Blocked)
• Long Crank Time (leaking)
• Oxygen Sensor/Mixture/Injector Related Fault Codes
Air Shroud Injector: To comply with emission regulations, Air Shrouded Injectors have
been fitted on the M42 engine since 1994 MY. There is an air gap between the inner and
outer body of the fuel injector which allows additional metered air to be drawn in. This air
disperses and mixes with the injected fuel which improves fuel atomization as it enters the
combustion chamber thus lowering CO/HC emissions.
13550017.jpg
The Air Shrouded Injectors incorporate a hose fitting on the outer injector body which connects each injector via a rubber hose, to the molded Idle Speed Control Valve hose, under
the intake manifold.
27
ST055 M1.7.2 Fuel Management
The metered air is taken from a fitting located in
the intake bellows boot in front of the throttle
valve (ported vacuum). The system is self regulating with greater air flow at idle and low load
engine ranges (intake manifold vacuum drawing
air in).
The Air Shrouded supply components are:
1.
Idle Speed Control Valve
2.
Connection to Intake Bellows Boot
3.
4.
Connection to Intake Manifold
Hoses for Air Shrouded Injectors
11550046.bmp
Crankshaft Position/RPM Sensor: This sensor provides the crankshaft position and engine speed (RPM)
signal to the ECM for Fuel Pump and Injector operation. This is an inductive pulse type sensor. The ECM
provides the power supply to this component.
67
The sensor scans an incremental impulse/gear wheel
that has a total of 58 teeth and a gap of two missing
teeth. The rotation of the impulse wheel generates an
A/C voltage signal in the sensor where-by each tooth
of the wheel produces one pulse. The ECM counts the
pulses and determines engine rpm.
The gap of two missing teeth provides a reference
point that the ECM recognizes as crankshaft position.
13550019.eps
The impulse wheel is mounted behind the
crankshaft pulley. The Sensor is mounted on
the front timing cover (housing).
A fault with this input will produce the following
complaints:
• No Start
• Intermitant Misfire / Driveability
• Engine Stalling
13550021.jpg
28
ST055 M1.7.2 Fuel Management
68
Camshaft Position Sensor (Cylinder Identification): The cylinder ID sensor (inductive
pulse) input allows the ECM to determine camshaft position in relation to crankshaft position. It is used by the ECM to establish the firing order for the direct ignition system and the
semi-sequential fuel injection timing.
The sensor scans a tooth mounted on the
intake camshaft drive gear (mounted in the front
of the cylinder head). The ECM provides the
power supply for this component and monitors
the A/C voltage generated when the tooth
passes the sensor tip. This input provides one
pulse per revolution of the camshaft.
This input is only checked by the ECM during
“start up”. The camshaft position is referenced
to the crankshaft position, and is not monitored
until the next engine start up.
13550011.eps
If the ECM detects a fault with the Cylinder ID Sensor, the “CHECK ENGINE” Light will be
illuminated and the system will still operate based on the Crankshaft Position/RPM Sensor.
Upon a restart, a slight change in driveability could occur because the ECM will activate
Parallel Fuel Injection, all of the injectors will be activated at the same time.
Engine Coolant Temperature: The Engine Coolant Temperature is provided to the ECM
from a Negative Temperature Coefficient (NTC) type sensor. The ECM determines the correct fuel mixture and base ignition timing required for the engine temperature.
The sensor decreases in resistance as the temperature rises and vice versa.
The ECM monitors an applied voltage to the
sensor (5v). This voltage will vary (0-5v) as
coolant temperature changes the resistance
value.
This sensor is located in the coolant jacket of
the cylinder head (1).
13550022.jpg
If the Coolant Temperature Sensor input is faulty, the “CHECK ENGINE” Light will be illuminated and the ECM will assume a substitute value (80º C) to maintain engine operation.
29
ST055 M1.7.2 Fuel Management
Throttle Position Sensor: The potentiometer is monitored by the ECM for throttle angle position and rate of
movement. For details about the sensor, refer to the Air
Management section.
M1.7.2
Control
Module
As the throttle is opened, the ECM will increase the volume of fuel injected into the engine. As the throttle
plate is closed, the ECM activates fuel shut off if the
rpm is above idle speed (coasting).
If the Throttle Position input is defective, a fault code
will be set and the “CHECK ENGINE” Light will illuminate. The ECM will maintain fuel injection operation
based on the Air Flow Volume Sensor and the
Crankshaft Position/RPM Sensor.
13550002-1.eps
Air Flow Volume Sensor: This potentiometer sends a
signal to the ECM representing the measured amount
of intake air volume. This input is used by the ECM to
determine the amount of fuel to be injected for correct
air/fuel ratio. For details about the sensor, refer to the
Air Management section.
If this input is defective, a fault code will be set and the
“CHECK ENGINE” Light will illuminate. The ECM will
maintain fuel injection operation based on the Throttle
Position Sensor and Crankshaft Position/RPM Sensor.
12550013-1.eps
Air Temperature: This signal allows the ECM to make
a calculation of air density. The sensor is located in
front of the measuring flap. For details about the sensor, refer to the Air Management section.
The varying voltage input from the NTC sensor indicates the larger proportion of oxygen found in cold air,
as compared to less oxygen found in warmer air. The
ECM will adjust the amount of injected fuel because the
quality of combustion depends on oxygen sensing
ratio.
If this input is defective, a fault code will be set and the
“CHECK ENGINE” Light will illuminate.
13550001.jpg
30
ST055 M1.7.2 Fuel Management
Principle of Operation
Fuel Management delivers fuel from the tank to the intake ports of the engine. To accomplish this, fuel supply must be available to the fuel injectors. Then the fuel must be injected in the precise amount and at the correct time. The ECM does not directly monitor fuel
supply, although it does control fuel supply. The Fuel Pump supplies fuel when it receives
operating voltage from the Engine Control Module Relay supplying the Fuel Pump Relay.
The ECM controls and monitors fuel injection.
12550014.eps
The Fuel Pump will be activated when
the igniton (KL15) is switched “on” and
the ECM supplies a ground circuit to
activate the Fuel Pump Relay. The Fuel
Pump Relay supplies operating power to
the in-tank mounted fuel pump. This is a
momentary activation to “pressurize”
(prime) the fuel system.
The ECM then requires an engine RPM
signal from the Crankshaft Position/RPM
Sensor to maintain continuous Fuel
Pump Relay activation.
If the engine RPM signal is not present,
the ECM will deactivate the Fuel Pump
Relay.
13550012.eps
The Fuel Injectors will be opened by the ECM to inject pressurized fuel into the intake
ports. The Fuel Injectors receive voltage from the Engine Control Module Relay. The ECM
controls the opening by activating the ground circuit for the Solenoid Windings. The ECM
will vary the duration (in milli-seconds) of “opening” time to regulate the air/fuel ratio.
31
ST055 M1.7.2 Fuel Management
The ECM has two Final Stage output transistors
that switch ground to the four injector solenoids.
The Injector “triggering” is first established from
the Crankshaft Position/RPM Sensor.
The ECM is programmed to activate the Final
Stage output transistors once for every revolution of the crankshaft (Parallel Injection). The
ECM calculates the total milli-second time to
open the injectors and cuts that value in half.
13550013.eps
The injectors are all opened at the same time (in
parallel) for every complete crankshaft revolution. This delivers half of the fuel charge at each Parallel Injection
injection so that the engine receives the full fuel 1
charge during a complete working cycle. This
process enhances fuel atomization during start 3
up.
4
During start up, the ECM recognizes the
Camshaft Position (Cylinder ID) input. It then
switches the injection to Semi-Sequential. This
process “times” the injection closer to the intake
valve opening for increased efficiency.
2
180
0
360
540
720
540
720
Injector Open
Intake Valve Open
When activated, each group (grouped in pairs) Semi-Sequential Injection
delivers the full fuel charge at separate times for 1
each engine working cycle.
3
The Camshaft Position input is only checked by
the ECM during start up. The camshaft position
is referenced to the crankshaft position, and is
not monitored until the next engine start up.
Therefore, if this input is lost when the engine is
already running, there will be no effect. There will
only be an effect if this input is missing when the
engine is started. For this condition, the ECM
will continue operating the injectors in Parallel.
32
ST055 M1.7.2 Fuel Management
4
2
0
180
360
Injector Open
Intake Valve Open
The Injector “open” Time to maintain engine operation after it has been started is determined by the ECM (programming). The ECM will calculate the engine “load” based on a
combination of the following inputs:
• Battery Voltage
• Throttle Position
• Air Flow Volume
• Air Temperature
Cylinder Id Signal
• Crankshaft Position/RPM
• Crankshaft Position (Cylinder ID)
• Engine Coolant
• Oxygen Sensor
(Detail in Emissions)
13550014.eps
The injection ms value will be regulated based on battery voltage. When cranking, the voltage is low and the ECM will increase the ms value to compensate for injector “lag time”.
When the engine is running and the battery voltage is higher, the ECM will decrease the
injection ms value due to faster injector reaction time.
Cold starting requires additional fuel to compensate for poor mixture and the loss of fuel as
it condenses onto cold intake ports, valves and cylinder walls. The cold start fuel quantity
is determined by the ECM based on the Engine Coolant Temperature Sensor input during
start up.
During cranking, additional fuel is injected (in Parallel) for the first few crankshaft revolutions.
After the first few crankshaft revolutions, the injected quantity is metered down as the
engine comes up to speed. When the engine speed approaches idle rpm, the ECM recognizes the Camshaft Position and switches to Semi-Sequential injection.
When the engine is cold, optimum fuel metering is not possible due to poor air/fuel mixing
and an enriched mixture is required. The Coolant Temperature input allows the ECM to
adjust the injection ms value to compensate during warm up and minimize the the injected fuel at engine operating temperature.
33
St055 M1.7.2 Fuel Management
When the engine is at idle, minimum injection is required. Additional fuel will be added if the
ECM observes low engine rpm and increasing throttle/air volume inputs (acceleration
enrichment). As the throttle is opened, the ECM monitors acceleration and rate of movement. The ECM will increase the volume of fuel injected into the engine by increasing the
injection ms value. The “full throttle” position indicates maximum acceleration and the ECM
will add more fuel (full load enrichment).
As the throttle is closed, the ECM decreases the injection ms value (fuel shut off) if the rpm
is above idle speed (coasting). This feature decreases fuel consumption and lowers emissions. When the engine rpm approaches idle speed, the injection ms value is increased
(cut-in) to prevent the engine from stalling. The cut-in rpm is dependent upon the engine
temperature and the rate of deceleration.
The Air Flow Volume signal provides the measured amount of intake air volume. This input
is used by the ECM to determine the amount of fuel to be injected to “balance” the air/fuel
ratio.
The Air Temperature Signal allows the ECM to make a calculation of air density. The varying voltage input from the NTC sensor indicates the larger proportion of oxygen found in
cold air, as compared to less oxygen found in warmer air. The ECM will adjust the amount
of injected fuel because the quality of combustion depends on oxygen sensing ratio (details
in Emissions).
The Crankshaft Position/RPM signals the ECM to start injection as well as providing information about the engine operation. This input is used in combination with other inputs to
determine engine load which increases/decreases the injection ms value. Without this input, the ECM will not activate the injectors.
The Camshaft Postion (Cylinder ID) affects the injection ms value (half= Parallel Injection or
full= Semi-Sequential Injection) and the timing when it is injected to the engine. To accomplish this, the ECM contains two Final Stage output transistors that activate the injectors in
two groups. The engine operates sufficiently on Parallel Injection, but more efficiently on
Semi-Sequential Injection. If one of the circuits faulted, the engine can still operate on limited power from the remaining circuit.
34
ST055 M1.7.2 Fuel Management
Injection “Reduction” Time is required to control fuel economy, emissions, engine and
vehicle speed limitation. The ECM will “trim” back or deactivate the fuel injection as necessary while maintaining optimum engine operation.
13550008.eps
As the throttle is closed during deceleration, the ECM decreases the injection ms value (fuel
shut off) if the rpm is above idle speed (coasting). This feature decreases fuel consumption
and lowers emissions.
When the engine rpm approaches idle speed, the
injection ms value is increased (cut-in) to prevent the
engine from stalling. The cut-in rpm is dependent upon
the engine temperature and the rate of deceleration.
This function can be observed as displayed on the Fuel
Economy (MPG) gage.
The ECM will deactivate the injectors to control maximum engine rpm (regardless of vehicle speed). When
the engine speed reaches 6500 rpm, the injectors will
be deactvated to protect the engine from over-rev. As
the engine speed drops below 6500 rpm, injector activation will be resumed. This feature does not protect the engine from a forced over-rev such as
improperly downshifting a manual transmission
equipped vehicle (driver error).
3
2
4
5
1/ min
x 1000
6
1
50
30 20
16
7
12
12550023.eps
Maximum vehicle speed is limited by the ECM reducing the injection ms value (regardless
of engine rpm). This limitation is based on the vehicle dimensions, specifications and installed tires (speed rating).
35
ST055 M1.7.2 Fuel Management
The ECM will also protect the Catalytic Converter by deactivating the injectors.
If the ECM detects a fault in the primary ignition system, it can selectively deactivate the
Final Stage output transistor for that cylinder.
The injector will not open, preventing unburned fuel from entering the exhaust system.
On the M1.7.2 system, there are two injectors per circuit resulting in deactivation of both.
This will limit engine power, but protect the Catalytic Converter.
Primary Activaton and Monitor
13550009.eps
36
ST055 M1.7.2 Fuel Management
Workshop Hints
Before any service work is performed on any fuel system related component,
always adhere to the following:
• Observe relevent safety legislation pertaining to your area.
• Ensure adequate ventilation.
• Use exhaust extraction system where applicable (alleviate fumes).
•
DO NOT OPERATE THE FUEL PUMP unless it is properly installed in the fuel tank and
is submersed in the fuel (fuel lubricates the pump).
•
DO NOT SMOKE while performing fuel system repairs.
• Always wear adequate protective clothing including eye protection.
• Use caution when working around a
HOT engine compartment.
• During fuel system repairs that involve “sealing rings”, always replace them with new copper
sealing rings only.
• BMW does not recommend any UNAUTHORIZED MODIFICATIONS to the fuel system.
The fuel system are designed to comply with strict federal safety and emissions regulations.
In the concern of product liability, it is unauthorized to sell or perform modifications to
customer vehicles, particularly in safety related areas.
• Always consult the REPAIR
before attempting a repair.
INSTRUCTIONS on the specific model you are working on
Fuel
Fuel quality should always be considered when diagnosing a driveability complaint. The
type of fuel, proper AKI rating, impurities and moisture are not factored by the ECM.
Please refer to the Owner’s Manual and following Service Information Bulletins regarding
fuel:
• Gasoline Fuel Quality S.I. #13 01 88 (1564)
• Gasoline Additive S.I. #13 04 88 (1591)
37
ST055 M1.7.2 Fuel Management
Fuel Supply
The fuel supply hardware should be visually inspected for damage that can affect pick- up,
transfer, pressure and return.
Please refer to the Repair Instructions and the following Service Information Bulletins details
on fuel supply hardware:
• Engine Compartment Return Fuel Hose S.I. #13 03 92 (3589)
• Feed Fuel Hose Recall Campaign S.I. #13 04 92 (3657)
• Refueling S.I. #16 01 92 (3553)
• Fuel System Modifications S.I. #16 01 81
Fuel Pump and Sending Unit Access
All BMW vehicles have access plates to service
the fuel pump and sending units without
removing the fuel tank.
The access plates are located under the rear
seat.
The “saddle” type fuel tank (under rear seat)
has two access plates.
13550027.eps
The passenger side allows access to the fuel
pump/sending unit.
The driver side allows access to the sending
unit.
13550028.eps
38
ST055 M1.7.2 Fuel Management
Draining the Fuel Tank
In order to remove the fuel tank it must be drained first
to avoid fuel spills and handling excessive weight. In
some cases depending on the fuel tank dimensions
(vehicle specific), it is also necessary to drain the fuel
tank to replace the sending units and/or fuel pump.
CAUTION: In some vehicles, the sending units/fuel
pump is mounted lower than the top of the fuel tank.
A fuel spill will be encountered if the fuel is not drained.
NOTE: Consult the BMW Service Workshop Equipment for the proper evacuation equipment.
The saddle type tank requires an additional step to
drain the fuel from the driver side. The evacuation
equipment should be attached to the tank compensating hose (arrow) to drain out the remaining fuel.
13550015.eps
Fuel Pump/Pressure Regulator - Testing
The fuel pump should be tested for delivery pressure
and volume. Caution when disconnecting fuel hoses
because there is the possibility of residual fuel pressure! Install the fuel pressure gage between the fuel filter and and pressure regulator.
Remove the fuel pump relay (see relay testing in the
power supply section) and connect the Relay Bypass
Switch to pin 87b and 30 of the relay socket. This will
activate the fuel pump without running the engine.
If the 3 bar fuel pressure is not achieved or bleed off is
more than 0.5 bar, refer to 13 31 of the Repair
instructions for further diagnosis. The Fuel Hose
Clamp Tool can be used to isolate bleed off from the
pump (non-return check valve) or the pressure regulator (restriction valve). Also verify power supply to the
fuel pump.
13550017.eps
39
ST055 M1.7.2 Fuel Management
Fuel volume must be tested to verify:
• Fuel Pump Output
• Restriction are not present in the pump pickup
lines/hoses and fuel filter
13550029.jpg
Fuel Injectors
When inspecting the fuel injectors, consider the
following:
• O-rings should be replaced, lubricated with
vaseline or SAE 90 gear oil for installation.
• Verify the code number
• Plastic spacer washer is not damaged
• Color code of nozzle hosing
• Color code injector housing
13550030.jpg
Fuel injectors can leak which bleeds off fuel
pressure and increases emissions. The injectors
can be tested using the Fuel Injector Leakage
Tester.
The fuel injectors can be cleaned, refer to
Service Information Bulletin S.I. #04 07 86.
13550031.gpg
40
ST055 M1.7.2 Fuel Management
The Fuel Injectors should also be tested using the DIS/MoDIC for:
• Resistance (15 - 17 ohms)
• Power Supply
+
• Status Display - Fuel Injection Signal
(approximate 3.5 - 5 ms)
• ECM Final Stage transistor activation. This test
function is found under the Oscilloscope
Preset list - “Ti Injection Signal”. Install the
88 pin adapter, Diagnostic cable, MFK 2
negative lead to ECM ground and MFK 2
positive lead to the ground activation cicuit
for the injector. This test is performed with
the engine running.
MFK 2
Negative MFK 2
Positive
13550010.eps
13550018.eps
41
ST055 M1.7.2 Fuel Management
Crankshaft Position/RPM Sensor
This sensor should be tested using the DIS/MoDIC for:
• Resistance (540 ohms +/- 10%)
• Power Supply
• AC Voltage • Status Display
• Oscilloscope Display found under Preset list - “Rotation Speed Sensor Signal”
67
68
13550019.jpg
12550011.eps
Camshaft Position Sensor (Cylinder ID)
This sensor should be tested using the DIS / MoDic for
• Resistance (0.1 - 1 ohm)
• Power Supply
• AC Voltage
• Status Display - “ON”
• Oscilloscope Display found under Preset list - “Rotation Speed Sensor Signal”
13550011.eps
42
ST055 M1.7.2 Fuel Management
07550002.eps
Engine Coolant Temperature
NTC sensors decrease in resistance as the temperature rises and vice versa. The ECM
monitors the sensor voltage which varies as temperature changes the resistance value. For
example, as temperature rises:
• Resistance through the sensor
decreases
• Voltage drop of the sensor
decreases
• Input signal voltage also
decreases (5-Ov)
78
43
The Sensor should be tested
using:
• DIS/Modic Status page
degrees C (dependent on engine
temperature).
• DIS/Modic Multimeter
20º C 2.2 - 2.7 K ohms
80º C 0.3 - 0.36 K ohms
13550012.eps
43
ST055 M1.7.2 Fuel Management
Tools and Equipment
The DIS/Modic as well as a reputable hand held
multimeter can be used when testing inputs/
components.
It is best to make the checks at the ECM connection, this method includes testing the wiring
harness.
The correct Universal Adapter for the M1.7.2
application should be used (#88 88 6 614 410).
This will ensure the pin connectors and the harness will not be damaged.
07550003.eps
The interior of this Universal Adapter is shielded,
therefore it is vital that the ground cable is connected to the vehicle chassis whenever the
adapter is used.
88 Pin
Adapter
The adapter uses a Printed Circuit board inside
keeping the capacitive and inductive load to a
minimum.
12550005.eps
When installing the Universal Adapter to the
ECM (located below the windshield on the passenger side of the engine compartment), make
sure the ignition is switched off.
The Fuel Hose Clamp Tool (#13 3 010) can be
used for isolating pressure faults. In addition,
fuel loss can be reduced when changing the
fuel filter while losening clamps (1 and 2).
The Relay Bypass Switch (#61 3 050) must be
used especially when fuel vapors are present! The switch eliminates the risk of electrical
arcing.
13550020.eps
44
ST055 M1.7.2 Fuel Management
When testing fuel pressure, the hand held fuel pressure
gage (#13 3 060) can be used.
Caution: Residual fuel pressure may be present!
The DIS is equipped with a pressure measuring function, found in Measurement testing. The following
adapters (Special Tool numbers) will be necessary:
• #13 6 051
• #13 6 055
• #13 6 057
These adapters install “in line” in the fuel pressure
hose.
13550021.eps
For vehicles equipped with “quick-release” couplings,
install special tool (#13 5 270) between the fuel filter (1)
and pressure supply hose (2). This tool will couple to
the DIS Pressure Adapter (3).
Later fuel rails are equipped with a threaded adapter
fitting (1).
This threaded adapter fitting allows Adapter #13 5 220
to be threaded on to the fuel rail and coupled to the
DIS Pressure Adapter.
13550022.eps
45
ST055 M1.7.2 Fuel Management
When testing the fuel injectors for leakage, use Special Tool #88 88 5 000 362. Leak testing the fuel injectors is one of the diagnostic steps listed in “Long Cranking Times” S.I. #13
08 90 (3096). This tool pressurizes the injectors with air and the injector tips are submersed
in water. If air bubles are present, this indicates the leaking injector(s).
13550032.jpg
46
ST055 M1.7.2 Fuel Management
Ignition Management
13550015.eps
Ignition Coils: The high voltage supply required to ignite the mixture in the combustion
chambers is determined by the stored energy in the ignition coils. The stored energy contributes to the ignition duration, ignition current and rate of high voltage increase. The Coil
circuit including primary and secondary components consists of:
1. Coil Assembly
• Primary Winding
• Secondary Winding (with diode)
2. Resistor (Boot Connector)
3. Spark Plug
4. ECM Final Stage Transistor
5. Secondary Coil Ground
12550011.eps
The Coil Assembly contains two copper windings insulated from each other. One winding
is the primary winding, formed by a few turns of thick wire. The secondary winding is
formed by a great many turns of thin wire.
The primary winding receives battery voltage from the ignition switch (Terminal 15). The
ECM provides a ground path for the primary coil (Terminal 1) by activating a Final Stage
transistor. The length of time that current flows through the primary winding is the “dwell”
which allows the coil to “saturate” or build up a magnetic field. After this storage process,
the ECM will interupt the primary circuit at the point of ignition by deactivating the Final
Stage transistor. The magnetic field built up within the primary winding collapses and
induces the ignition voltage in the secondary winding.
47
ST055 M1.7.2 Ignition Management
The voltage generated in the secondary winding is capable of 30,000 volts (30 KV). The
high voltage is discharged (Terminal 4) through the secondary ignition cable and resistor
(boot connector) to the spark plug.
The primary and secondary windings are uncoupled, therefore, the secondary winding
requies a ground supply (Terminal 4a).
The secondary winding connects to a cascade
diode which suppresses any unwanted induced
voltages as the primary circuit is switched on
and off. This permits a clean, high voltage discharge from the secondary winding.
There is an individual ignition circuit and coil for
each cylinder on the M1.7.2 system
12550012.eps
The four ignition coils are combined into a single component (coil pack) located on the right front strut tower.
The ignition primary circuits are fault monitored by the
ECM. If a fault is present, the “CHECK ENGINE” Light
will illuminate and the ECM will deactivate the corresponding fuel injector for that cylinder and engine operation will still be possible.
Ignition Leads: The secondary ignition cables (high
tension leads) direct the high voltage from the ignition
coils to the spark plugs. The ignition lead assembly
consists of:
13550026.eps
• Connector Socket
• Ignition Cable
• Resistive Adaptive Boot
The ignition cables are routed into a covered
cable tray located on the top of the cylinder
head, which contains the boot connector
removal tool (arrow).
13550013.bmp
48
ST055 M1.7.2 Ignition Management
Spark Plugs: The spark plugs introduce the
ignition energy into the combustion chamber.
The high voltage “arcs” across the air gap in the
spark plug from the positive electrode to the
negative electrode. This creates a spark which
ignites the combustable air/fuel mixture.
The spark plugs are located in the center of the
combustion area (on the top of the cylinder
head) which is the most suitable point for igniting the compressed air/fuel mixture.
The correct spark plugs (as seen above right) for
this system are:
13550014.eps
• Bosch F7LDCR (dual electrode, non-adjustable gap)
• NGK BKR7EK (dual electrode, non-adjustable gap)
Note: The High Performance Platinum Spark Plugs are also approved for use.
Faults with the Ignition Output Components are not monitored by the ECM, with the
exception of the primary ignition circuit. If there are faults with the igniton coil(s) output, ignition leads and/or spark plugs, the following complaints could be encountered:
• “CHECK ENGINE” Light With Mixture Related Fault Codes
• Poor Engine Performance
• Engine Misfire
• No Start / Hard Starting
• Excessive Exhaust Emissions / Black Smoke
The Ignition Output Components must be individually tested (see Workshop Hints)
49
ST055 M1.7.2 Ignition Management
Knock Sensors: are required to prevent detonation (pinging) from damaging the engine.
The Knock Sensor is a piezoelectric conductor-sound microphone. The ECM will retard the
ignition timing (cylinder selective) based on the input of these sensors. Detonation can
occur due to:
• High Compression Ratio
• Maximum Timing Advance Curve
• Poor Quality Fuel (Octane Rating)
• High Intake Air and Engine Temperature
• High Level of Cylinder Filling
• Carbon Build-Up (Combustion Chamber)
The Knock Sensor consists of:
1.
2.
3.
4.
5.
6.
Shielded Wire
Cup Spring
Seismic Mass
Housing
Inner Sleeve
Piezo-Ceramic Element
13550005.bmp
A piezo-ceramic ring is clamped between a seismic mass and the sensor body. When the
seismic mass senses vibration (flexing), it exerts a force on the peizo-ceramic element.
Opposed electrical charges build up on the upper and lower ceramic surfaces which generates a voltage signal. The acoustic vibrations are converted into electrical signals. These
low voltage signals are transmitted to the ECM for processing.
There are two Knock Sensors bolted to the
engine block (1) between cylinders 1 & 2 and (2)
between cylinders 3 & 4. If the signal value
exceeds the threshold, the ECM identifies the
“knock” and retards the ignition timing for that
cylinder.
If a fault is detected with the sensors, the ECM
deactivates Knock Control. The “CHECK ENGINE” Light will be illuminated, the ignition timing
will be set to a conservative basic setting and a
fault will be stored.
50
ST055 M1.7.2 Ignition Management
13550001.bmp
Crankshaft Position/RPM Sensor: This sensor provides the crankshaft position and
engine speed (RPM) signal to the ECM for ignition activation and correct timing. For details
about the sensor, refer to the Fuel Management section.
A fault with this input will produce the following complaints:
• No Start
• Intermitant Misfire/Driveabilty
• Engine Stalling
13550027.eps
Camshaft Position Sensor (Cylinder Identification): The cylinder ID sensor (inductive
pulse) input allows the ECM to determine camshaft position in relation to crankshaft position. It is used by the ECM to establish the “working cycle” of the engine for precise ignition timing. For details about the sensor, refer to the Fuel Management section.
If the ECM detects a fault with the Cylinder ID Sensor,
the “CHECK ENGINE” Light will be illuminated and the
system will still operate based on the Crankshaft
Position/RPM Sensor.
Upon a restart, a slight change in driveability could
occur because the ECM will activate “double ignition”. The ignition coils will be activated on both the
compression and exhaust strokes to maintain engine
operation.
13550028.eps
51
ST055 M1.7.2 Ignition Management
Engine Coolant Temperature: The ECM determines
the correct ignition timing required for the engine temperature. For details about the sensor, refer to the Fuel
Management section. This sensor is located in the
coolant jacket of the cylinder head (1).
1
If the Coolant Temperature Sensor input is faulty, the
“CHECK ENGINE” Light will be illuminated and the
ECM will assume a substitute value (80º C) to maintain
engine operation. The ignition timing will be set to a
conservative basic setting.
Throttle Position Sensor: This sensor provides the
ECM with throttle angle position and rate of movement.
For details about the sensor, refer to the Air Management section.
13550002.bmp
As the throttle plate is opened, this requests acceleration and at what rate. The ECM will advance the ignition timing. The “full throttle” position indicates maximum acceleration to the ECM, the ignition will be
advanced for maximum torque.
If the Throttle Position input is defective, a fault code
will be set and the “Check Engine” Light will illuminate.
The ECM will maintain engine operation based on the
Air Flow Volume Sensor and the Engine Speed Sensor,
and the ignition timing will be set to a conservative
basic setting.
13550013.eps
Air Flow Volume Sensor: This signal to the ECM represents the measured amount of intake air volume.
This input is used by the ECM to determine the amount
of ignition timing advance. For details about the sensor,
refer to the Air Management section.
If this input is defective, a fault code will be set and the
“Check Engine” Light will illuminate. The ECM will
maintain engine operation based on the Throttle
Position Sensor and Engine Speed Sensor, and the
ignition timing will be set to a conservative basic setting.
52
ST055 M1.7.2 Ignition Management
13550004.bmp
Air Temperature: This signal allows the ECM to make
a calculation of air density. The sensor is located in
front of the measuring flap. For details about the sensor, refer to the Air Management section.
The ECM will adjust the ignition timing based on air
temperature. If the intake air is hot the ECM retards the
ignition timing to reduce the risk of detonation. If the
intake air is cooler, the ignition timing will be advanced.
If this input is defective, a fault code will be set and the
“Check Engine” Light will illuminate. The ignition timing
will be set to a conservative basic setting.
13550033.jpg
53
ST055 M1.7.2 Ignition Management
Principle of Operation
Ignition Management provides ignition to the combustion chambers with the required voltage at the correct time. Based on the combination of inputs, the ECM calculates and controls the ignition timing and secondary output voltage by regulating the activation and
dwell of the primary ignition circuit. The ECM does not directly monitor secondary ignition output, although it does control and monitor the primary ignition circuit.
12550015.eps
The ECM has a very “broad” range of ignition timing. This is possible by using a Direct
Ignition System, or sometimes refered to as “Static Ignition System”. Reliability is also
increased by having separate individual ignition circuits.
The Ignition Control is determined by the ECM (load dependant). The ECM will calculate
the engine “load” based on a combination of the following inputs:
• Battery Voltage
• Throttle Position
• Air Flow Volume
• Air Temperature
• Engine Coolant
• Crankshaft Position/RPM
• Camshaft Position (Cylinder ID)
• Knock Sensors
The dwell time will be regulated based on battery voltage. When cranking, the voltage is
low and the ECM will increase the dwell to compensate for saturation “lag time”. When the
engine is running and the battery voltage is higher, the ECM will decrease the dwell due to
faster saturation time.
The Crankshaft Position/RPM signals the ECM to start ignition in firing order (1-3-4-2) as
well as providing information about the engine operation. This input is used in combination
with other inputs to determine engine load which advances/retards the ignition timing.
Without this input, the ECM will not activate the ignition.
54
ST055 M1.7.2 Ignition Management
Cold start is determined by the ECM based on the engine coolant temperature and rpm
during start up. A cold engine will crank over slower than a warm engine, the ignition timing will range between top dead center to slightly retarded providing optimum starting.
When starting a warm engine, the rpm is higher which results in slightly advanced timing.
If the engine coolant and intake air temperature is hot, the ignition timing will not be advanced reducing starter motor “load”.
During cranking, the ECM recognizes the Camshaft Position
(compression stroke) and activates a single ignition per cylinder.
If this signal is not recognized, the
ECM will activate “Double Ignition”. The ignition coils will be
activated on both the compression and exhaust strokes to
maintain engine operation. The
ignition timing will be progressively ad-vanced asisting the engine
in coming up to speed.
As the engine speed approaches
idle rpm, the timing remains slightly advanced to boost torque.
When the engine is at idle speed,
minimum timing advance is required. This will allow faster engine and catalyst warm up.
13550030.eps
The timing will be advanced when the ECM observes low engine rpm and increasing throttle/air volume inputs (acceleration torque). As the throttle is opened, the ECM advances the
timing based on engine acceleration and at what rate. The ECM will fully advance timing for
the “full throttle” position indicating maximum acceleration (torque).
The Air Flow Volume signal provides the measured amount of intake air volume. This input
is used by the ECM to determine the amount of timing advance to properly combust the
air/fuel mixture.
55
ST055 M1.7.2 Ignition Management
The Air Temperature Signal assists the ECM in reducing the risk of detonation (ping). If the
intake air is hot the ECM retards the igniton timing. If the intake air is cooler, the ignition timing will be advanced.
As the throttle is closed, the ECM decreases the ignition timing if the rpm is above idle
speed (coasting). This feature lowers the engine torque for deceleration. When the engine
rpm approaches idle speed, the timing is slightly advanced to prevent the engine from
stalling. The amount of advance is dependent upon the engine temperature and the rate of
deceleration.
Knock Control
The use of Knock Control allows the ECM to further advance the ignition timing under load
for increased torque. This system uses two Knock Sensors located between cylinders 1 &
2 and between cylinders 3 & 4.
Knock Control is only in affect when the engine temperature is greater than 35 ºC and there
is a load on the engine. This will disregard false signals while idling or from a cold engine.
Based on the firing order, the
ECM monitors the Knock
Sensors after each ignition for a
normal (low) signal.
If the signal value exceeds the
threshold, the ECM identifies the
“knock” and retards the ignition
timing (3º) for that cylinder the
next time it is fired.
This process is repeated in 3º
increments until the knock ceases. The ignition timing will be
advanced again in increments
right up to the knock limit and
maintain the timing at that point.
13550010.jpg
If a fault is detected with the Knock Sensor(s) or circuits, the ECM deactivates Knock
Control. The “CHECK ENGINE” Light will be illuminated, the ignition timing will be set to a
conservative basic setting (to reduce the risk of detonation) and a fault will be stored.
56
ST055 M1.7.2 Ignition Management
Workshop Hints
Before any service work is performed on any ignition system related component,
always adhere to the following:
• Observe relevent safety legislation pertaining to your area
• Always wear adequate protection clothing including eye protection.
• Use caution when working around a HOT engine compartment.
• Always consult the REPAIR INSTRUCTIONS on the specific model you are working on before
attempting a repair.
• Always SWITCH OFF THE IGNITION (KL15) before working on the ignition system.
• Use only BMW approved test leads.
• NEVER TOUCH COMPONENTS CONDUCTING CURRENT with the engine running.
• Do not connect suppression devices or a “test light” to terminal 1 of the ignition coils.
• Terminal 1 from the ignition coil to the ECM (High Voltage approximately 350 V)
HIGH VOLTAGE - DANGER!
Caution! Hazardous voltages occur at:
• Ignition Leads
• Spark Plug Connector
• Spark Plug
• Ignition Coil (High Voltage at terminal 4 is approximately 30 KV)
• Terminal 1 from the ignition coil to the ECM (High Voltage approximately 350V)
57
ST055 M1.7.2 Ignition Management
Ignition System Diagnosis
A fault survey should first be performed using the DIS/MoDIC to determine if there is a fault
in the primary ignition or secondary ignition.
If there is a fault in the primary ignition, testing should include:
• Power Supply at the Coil (KL15)
• Resistance of the harness and ignition coil primary winding (terminal 15 to 1 approximate 0.8
ohms) - using the 88 Pin Adapter with the ECM Disconnected
• ECM Primary Circuit Final Stage Transistor
• ECM Ignition Coil (one of four)
• Secondary Coil Ground
13550034.eps
• ECM Final Stage transistor activation. This
test function is found under the Oscilloscope
Preset list - “Ignition Signal Primary” (normal
Terminal 1 Signal shown on the right).
Install the 88 Pin Adapter, Diagnostic cable,
MFK 2 negative lead to ECM ground and
MFK 2 positive lead to the ground activation
circuit for Terminal 1 of the ignition coil. This
test is performed with the engine running.
13550017.bmp
58
ST055 M1.7.2 Ignition Management
If there is a fault in the secondary ignition, testing should include:
• Primary Ignition
• Evaluation of Secondary Oscilloscope Patterns
The Following are Examples of Secondary
Oscilloscope Patterns:
This is a normal pattern for one ignition circuit
with the engine at idle speed.
1. Normal Combustion Period
2. Normal Ignition Voltage Peak
07550001.bmp
Long Spark Period (1) with Low Ignition Voltage
Peak (2)
• Indicates Low Compression
If Spark Period is Fluctuating:
• Contamination on Spark Plug or Defective
Spark Plug
07550002.bmp
Short Spark Period (1) with High Ignition
Voltage Peak (2).
• Defective Ignition Cable, Connector, or
Resistive Adapter Boot
07550003.bmp
59
ST055 M1.7.2 Ignition Management
Evaluation of Ignition Voltage Peaks at Idle
Speed (All Cylinders Displayed).
• Normal Attenuation (Voltage Reduction) Process
• Shorten Attenuation Process-Defective Ignition
Coil
• Abscence of Attenuation - Defective Ignition Coil
07550004.bmp
No Sparking Voltage Line (Single Cylinder
Displayed)
• Defective Ignition Coil
07550005.bmp
Evaluation of Ignition Voltage Peaks under
Sudden Loads (All Cylinders Displayed).
• Decaying Process is not much Higher than
Ignition Voltage Peak - System is Ok.
• Decaying Process is considerably Higher
than Ignition Voltage Peak:
• Lean Mixture
• Defective Fuel Injector
• Low Compression
07550006.bmp
60
ST055 M1.7.2 Ignition Management
The Repair Instructions should be consulted for additional Oscilloscope Patterns under various engine speeds.
In Summary,
If the Secondary Ignition Voltage is Too High (Excessive Resistance for Ignition):
• Spark Plug Gap is to Large (Worn or Burned)
• Incorrect Heat Range Spark Plug
• Compression is too High (Carbon, etc.)
• Lean Mixture (Vacuum Leak, etc.)
• Interruption in the Secondary Ignition Cable, Connector, or Resistive Adapter Boot
If the Secondary Ignition Voltage is Too Low (Low Resistance for Ignition):
• Spark Plug Gap is Too Small (Mishandled on Installation)
• Incorrect Heat Range Spark Plug
• Compression is Too Low
• Voltage Leak in the Secondary Ignition Cable, Connector, or Resistive Boot to Ground
Spark Plugs
The Spark Plugs should be inspected for the
proper type, gap and replaced at the specified
intervals.
Refer to the Service Information Bulletin S.I. #12
01 99 for the proper type and a visual of the
spark plug (showing effects of combustion,
fouling, etc.)
13550014.bmp
61
ST055 M1.7.2 Ignition Management
Ignition Leads
The secondary ignition cable (high tension lead)
assembly includes the Connector Socket, Ignition Cable and Resistive Adapter Boot. These
components should be visually inspected and
checked for resistance.
For example, the Resistive Adapter Boot has a
different ohmic value depending on the manufacturer:
• Bosch - 1k ohm +/- 20%
• Bremi - 1.8k ohm +/- 20%
13550035.eps
Knock Sensors
The Knock Sensors should be tested using the
DIS/MoDIC for:
• Fault Codes
• Status Display - Knock Control
(active / not active)
• Oscilloscope Display (Low DC Voltage - mV
setting)
13550010.jpg
When installing Knock Sensors:
DO NOT MIX THE CONNECTORS: Engine
Damage will result! - the connector is critical to
sensor location (1) cylinder 1 & 2 and (2) cylinder
3 & 4.
Do Not Over Tighten attaching bolt! - Piezo
ceramic will be cracked. Torque to 20 nm.
Do Not Under Tighten attaching bolt, a lose
sensor can vibrate producing a similar signal to
a knock.
62
ST055 M1.7.2 Ignition Management
13550015.bmp
Tools and Equipment
The DIS/Modic as well as a reputable hand held
multimeter can be used when testing
inputs/components.
It is best to make the checks at the ECM connection, this method includes testing the wiring
harness.
The correct Universal Adapter for the M1.7.2
application should be used (#88 88 6 614 410).
This will ensure the pin connectors and the harness will not be damaged.
07550003.eps
The interior of this Universal Adapter is shielded,
therefore it is vital that the ground cable is connected to the vehicle chassis whenever the
adapter is used.
The adapter uses a Printed Circuit board inside
keeping the capacitive and inductive load to a
minimum.
88 Pin
Adapter
12550005.eps
When installing the Universal Adapter to the
ECM (located below the windshield on the passenger side of the engine compartment), make
sure the ignition is switched off.
When Testing the Secondary Ignition System,
use the High Tenision clip of the DIS. Refer to
the HELP button for additional (on screen) connections.
Caution!
Observe Safety Precautions, High Voltage
is Present with the Engine Running.
13550016.bmp
63
ST055 M1.7.2 Ignition Management
The secondary ignition cables, connectors and
sockets can be replaced separately.
12 1 081
New connectors can be “crimped” on using
Special Tool #12 1 081. This tool provides a two
stage crimp, crimping the core conductor (1)
and the insulator (2).
13550018.bmp
The connector with ignition cable should be
installed into the Resistive Adapter Boot with
Special Tools #12 1 087 and #12 1 086 to
ensure the connector properly “seats”.
`
13550019.bmp
The Spark Plugs should be properly installed
and torqued using the following Special Tools:
• 12 1 200 Torque Adapter
(prevents over tightening)
• 12 1 171 Spark Plug Socket
NOTE: NEVER USE AIR TOOLS FOR REMOVAL OR INSTALLATION!
13550020.bmp
64
ST055 M1.7.2 Ignition Management
Emissions Management - HC II Compliant (as of 96 MY)
18550000eps
1. Liquid/Vapor Seperator
3. ECM Relay
5.ECM
2. Active Carbon Canister
4. Evaporative Emission Valve
Evaporative Emissions: The control of the evaporative fuel vapors (Hydrocarbons) from
the fuel tank is important for the overall reduction in vehicle emissions. The evaporative system has been combined with the ventilation of the fuel tank, which allows the tank to breath
(equalization). The overall operation provides:
• An inlet vent, to an otherwise “sealed” fuel tank, for the entry of air to replace the fuel
consumed during engine operation.
• An outlet vent with a storage canister to “trap and hold” fuel vapors that are produced
by the expansion/evaporation of fuel in the tank, when the vehicle is stationary.
The canister is then "purged" using the engine vacuum to draw the fuel vapors into the
combustion chamber. This "cleans" the canister allowing for additional storage. Like any
other form of combustible fuel, the introduction of these vapors on a running engine must
be controlled. The ECM controls the Evaporative Emission Valve which regulates purging of
evaporative vapors.
65
ST055 M1.7.2 Emissions Management
Liquid/Vapor Separator: Fuel vapors are routed from the fuel tank filler neck through a hose
to the Liquid/Vapor Separator (located in the
right rear wheel well behind the trim). The
vapors cool when exiting the fuel tank, the condensates separate and drain back to the fuel
tank through a return hose (1). The remaining
vapors exit the Liquid/ Vapor Separator to the
Active Carbon Canister.
Active Carbon Cannister: As the hydrocarbon vapors enter the canister, they will be
absorbed by the active carbon. The remaining
air will be vented to the atmosphere through the
end of the canister allowing the fuel tank to
“breath”.
When the engine is running, the canister is then
"purged" using intake manifold vacuum to draw
air through the canister which extracts the
hydrocarbon vapors into the combustion chamber. The Active Carbon Canister is located in the
engine compartment on the left strut tower
(spare tire well on late 95 MY).
135500147.eps
Vent
135500147.eps
Evaporative Emission Valve: This ECM controlled solenoid valve regulates the purge flow
from the Active Carbon Canister into the intake
manifold (located next to the Air Volume Mass
Meter).
The ECM Relay provides operating voltage, and
the ECM controls the valve by regulating the
ground circuit. The valve is powered closed and
opened by an internal spring.
If the Evaporative Emission Valve circuit is
defective, a fault code will be set and the
“CHECK ENGINE” Light will illuminate. If the
valve is “mechanically” defective, a driveability
complaint could be encountered and a mixture
related fault code will be set.
66
ST055 M1.7.2 Emissions Management
18550001.eps
12550016.eps
Exhaust Emissions: The combustion process of a gasoline powered engine produces
Carbon Monoxide (CO), Hydrocarbons (HC) and Oxides of Nitrogen (NOx).
• Carbon Monoxide is a product of incomplete combustion under conditions of air deficiency.
CO emissions are strongly dependent on the air/fuel ratio.
• Hydrocarbon are also a product of incomplete combustion which results in unburned fuel. HC
emissions are dependent on air/fuel ratio and the ignition of the mixture.
• Oxides of Nitrogen are a product of peak combustion temperature (and temperature duration).
NOx emissions are dependent on internal cylinder temperature affected by the air/fuel ratio
and ignition of the mixture.
Control of exhaust emissions is accomplished by the engine and engine management
design as well as after-treatment.
• The ECM manages exhaust emissions by controlling the air/fuel ratio and ignition.
• The Catalytic Converter further reduces exhaust emissions leaving the engine.
67
ST055 M1.7.2 Emissions Management
Bosch Oxygen Sensor: The oxygen sensor measures the residual oxygen content of the
exhaust gas. The sensor produces a low voltage (0-1000 mV) proportional to the oxygen
content that allows the ECM to monitor the air/fuel ratio. If necessary, the ECM will “correct” the air/fuel ratio by regulating the ms injection time. The sensor is mounted in the hot
exhaust stream directly in front of the catalytic converter.
Ambient Air
1 2 3 4
5
6
7
8
9
10
( +)
Exhaust
Stream
12
( )
11
12550017.eps
1. Electrode (+)
2. Electrode (-)
7. External Body (Ventilated)
8. Contact Spring
3. Porous Ceramic Coating (Encasing Electrolyte)
4. Protective Metal Cage (Ventilated)
9. Vent Opening
10. Output Lead
5. Casing
11. Insulator
6. Contact Sleeve
12. Exhaust
The “tip” of the sensor contains a microporous platinum coating (electrodes) which conduct
current. The platinum electrodes are separated by solid electrolyte which conducts oxygen
ions.
The platinum conductors are covered with a highly porous ceramic coating and the entire
tip is encased in a ventilated metal “cage”. This assembly is submersed in the exhaust
stream. The sensor body (external) has a small vent opening in the housing that allows
ambient air to enter the inside of the tip.
The ambient air contains a constant level of oxygen content (21%) and the exhaust stream
has a much lower oxygen content. The oxygen ions (which contain small electrical charges)
are “purged” through the solid electrolyte by the hot exhaust gas flow. The electrical
charges (low voltage) are conducted by the platinum electrodes to the sensor signal wire
that is monitored by the ECM.
68
ST055 M1.7.2 Emissions Management
18550002.eps
If the exhaust has a lower oxygen content (rich mixture), there will be a large ion “migration”
through the sensor generating a higher voltage (950 mV). If the exhaust has a higher oxygen content (lean mixture), there will be a small ion “migration” through the sensor generating a lower voltage (080 mV).
This voltage signal is constantly changing due
to combustion variations and normal exhaust
pulsations.
This conductivity is efficient when the oxygen
sensor is hot (250º - 300º C). For this reason,
the sensor contains a heating element. This
“heated” sensor reduces warm up time, and
retains the heat during low engine speed when
the exhaust temperature is cooler.
1
0.9
Voltage
The ECM monitors the length of time the sensor
is operating in the lean, rich and rest conditions.
The evaluation period of the sensor is over a
predefined number of oscillation cycles.
Rest Time
t Rest Rich
RICH
0.8
0.7
0.6
0.5
LEAN
0.4
0.3
0.2
0.1
0
0
0.5
1
1.5
2
2.5
3
3.5
4
t Rest Lean1
4.5
Time
5
5.5
6
6.5
7
7.5
8
8.5
9
t Rest Lean2
13550011.eps
Heated Element
12550018.eps
69
ST055 M1.7.2 Emissions Management
Catalytic Converter: The three-way catalyst after-treats exhaust emissions leaving the
engine. A properly operating catalyst consumes most of the oxygen that is present in the
exhaust gas which is a result of burning the remaining pollutants. The oxygen sensor monitors the air/fuel mixture which allows the ECM to maintain the correct mixture for catalyst
efficiency. The gases that flow into the catalyst are converted from CO, HC and NOx to
CO2, H2O and N2 respectively.
The catalytic converter (monolith) is made of
thousands of small ceramic blocks that the
exhaust must flow through. The entire ceramic
structure is supported in the shell by a flexible
mat and wire mesh layer.
Coating of a 3-way catalytic converter:
platinum, rhodium
Wash coat
Ceramic or metal monolith body
Chemical reaction
The ceramic is coated with the precious metals
Platinum which speeds up oxidation of HC and
CO and Rhodium which speeds up the reduction of NOx.
The exhaust flow heats the catalyst and with the
remaining oxygen, the exhaust pollutants are
further reduced by burning. The temperature
operating range for the highest efficiency is
400º - 800º C which is also influenced by the
air/fuel mixture.
The M1.7.2 system uses the redesign catalytic
converter which distributes the exhaust gas uniformly as it enters the converter through a lateral discharge inlet.
This design allows the exhaust gas to strike the
entire surface of the monolith to ensure that
emissions from the exhaust system are reduced
to a consistenly low level.
70
ST055 M1.7.2 Emissions Management
HC
O
+C
Ox
+N
18550000.eps
HC + CO + NOx
H20
C02
N2
135500150.eps
Principle of Operation
Emissions Management controls evaporative and exhaust emissions. The ECM controls
the purging of evaporative fuel. The ECM monitors and controls the exhaust emissions by
regulating the combustable mixture. The catalytic converter after-treats by further breaking down remaining combustable exhaust gasses.
12550016.eps
Evaporative Emission Purging is regultated by the ECM controlling the Evaporative
Emission Valve. The Evaporative Emission Valve is a solenoid that regulates purge flow from
the Active Carbon Cannister into the intake manifold. The ECM Relay provides operating
voltage and the ECM controls the valve by regulating the ground circuit. The valve is powered closed and opened by an internal spring. The “purging” process takes place when:
• Oxygen Sensor Control is active
• Engine Coolant Temperature is >60ºC
• Engine Load is present
The Evaporative Emission Valve is opened in stages to moderate the purging.
• Stage 1 opens the valve for 10 ms (milli-seconds) and then closes for 150 ms.
• The Stages continue with increasing opening times (up to 16 stages) until the valve is
completely open.
• The Valve now starts to close in 16 stages in reverse order.
• This staged process takes 6 minutes to complete. The function is inactive for 1 minute
then starts the process all over again.
• During the purging process the valve is completely opened during full throttle operation
and is completely closed during deceleration fuel cutoff.
Evaporative Purge System Flow Check (1996 MY - HC II Emission Compliance) is
performed by the ECM when the oxygen sensor control and purging is active. When the
Evaporative Emission Valve is open the ECM detects a lean/rich shift as monitored by the
oxygen sensors indicating the valve is functioning properly. If the ECM does not detect a
lean/rich shift, a second step is performed when the vehicle is stationary and the engine is
at idle speed. The ECM opens and close the valve (abruptly) several times and monitors
the engine rpm for changes. If there are no changes, a fault code will be set.
71
ST055 M1.7.2 Emissions Management
Fuel System Monitoring is performed by the ECM which verifies
the calculated injection time (ti) in
relation to engine speed, load
and the oxygen sensor signal as
a result of the residual oxygen in
the exhaust stream.
The ECM uses the oxygen sensor
signal as a correction factor for
adjusting and optimizing the mixture pilot control under all engine
operating conditions.
135500144.eps
Adaptation Values are stored by the ECM iIn order to maintain an "ideal" air/fuel ratio.
The ECM is capable of adapting to various environmental conditions encountered while the
vehicle is in operation (changes in altitude, humidity, ambient temperature, fuel quality, etc.).
The adaptation can only make slight corrections and can not compensate for large
changes which may be encountered as a result of incorrect airflow or incorrect fuel supply
to the engine.
Within the areas of adjustable adaption, the ECM modifies the injection rate under two
areas of engine operation:
• During idle and low load mid range engine speeds (Additive Adaptation).
• During operation under a normal to higher load when at highter engine speeds
(Multiplicative Adaptation).
These values indicate how the ECM is compensating for a less than ideal initial air/fuel ratio.
NOTE: If the adaptation value is greater than "0.0 ms" the ECM is trying to richen the mixture. If the adaptation value is less then "0.0 ms” the ECM is trying to lean-out the mixture.
72
ST055 M1.7.2 Emissions Management
Oxygen Sensor Heating is controlled by the ECM to reduce
warm up time and retain heat
during low engine rpm when the
exhaust temperature is cooler.
Voltage is supplied from the
Oxygen Sensor Heater Relay and
the ground circuit for the relay is
provided by the ECM when
engine rpm is present.
During full throttle operation electrical heating is not required and
is deactivated by the ECM.
12550009.bmp
Oxygen Sensor Heater Relay Monitoring is checked separately for electrical integrity
and operation. The Heater Relay function is monitored continuously while the vehicle is in
closed loop operation, during activation by the ECM.
An improperly/non operating Heater Relay will not allow the sensor signal to reach its predefined maximum and minimum thresholds which can:
• Result in delayed closed loop operation causing an impact on emission levels.
• Result in increased emission levels while in closed loop operation.
As part of the monitoring function for Heater Relay current and voltage, the circuit is also
checked for an open, short to ground and short to B+ depending on the values of the current or voltage being monitored. If the power of the Heater Relay is not within a specified
range, a fault will be set and the “CHECK ENGINE" light will be illuminated.
73
ST055 M1.7.2 Emissions Management
The “CHECK ENGINE” Light required for OBD is located in the instrument cluster and is
activated by the ECM under the following conditions:
• Ignition “on” (KL15) and engine not runningbulb check function.
• A component malfunction that affects the
vechicle emissions.
• An Implausible input signal is generated
• Manufacturer-defined specifications are
exceeded.
• ECM fails to enter oxygen sensor closed-loop
control within a specified time interval.
UNLEADED GASOLINE
ONLY
CHECK
ENGINE
CHECK
CONTROL
ABS
BRAKE
FLUID
PARK
BRAKE
CHECK
ENGINE
135500146.eps
The ECM illuminates the “CHECK ENGINE” Light by activating a final stage transistor to
supply a ground circuit (arrow). The light has voltage supplied whenever KL15 is switched
“on”.
12550023.bmp
74
ST055 M1.7.2 Emissions Management
Workshop Hints
Before any service work is performed on any fuel system related component, always adhere to the following:
• Observe relevent safety legislation pertaining to your area.
• Ensure adequate ventilation.
• Use exhaust extraction system where applicable (alleviate
fumes).
• DO NOT SMOKE while performing fuel system repairs.
• Always wear adequate protection clothing including eye
protection.
• Use caution when working around a HOT engine compartment.
• BMW does not recommend any UNAUTHORIZED
MODIFICATIONS to the fuel system. The fuel systems are
designed to comply with strict Federal Safety and Emissions
Regulations. In the concern of product liabilty, it is
unauthorized to sell or perform modifications to customer
vehicles, particularly in safety related areas.
• Always consult the REPAIR INSTRUCTIONS on the specific
model you are working on before attempting a repair.
The “CHECK ENGINE” Light also has flash code readouts
that allows Technicians without BMW Special Tools or
Equipment to Diagnose an emission system failure.
For more information and ordering procedure for the OnBoard Emission System Diagnostic Guide refer to Service
Information Bulletin SI #13 08 88 (1718).
CHECK
ENGINE
75
ST055 M1.7.2 Emissions Management
Oxygen Sensor Wiring Harness Voluntary Recall Campaign No. 98E-A02 pertains to
oxygen sensor harness breakage due to the retainer clips (1 and 2). For more information
and details, refer to Service Information Bulletin SI # 11 03 98.
04550002.bmp
04550003.bmp
Testing the Oxygen Sensor should be performed using the DIS Oscilloscope from the
“Preset” List. The scope pattern should appear as below for a normal operating sensor.
If the signal remains high (rich
condition) the following should be
checked:
• Fuel Injectors
• Fuel Pressure
• Ignition System
If the signal remains low (lean
condition) the following should be
checked:
1
0.9
Voltage
• Input Sensors that influence
air/fuel mixture
• Engine Mechanical
Rest Time
t Rest Rich
RICH
0.8
0.7
0.6
0.5
LEAN
0.4
0.3
0.2
0.1
0
0
0.5
1
1.5
• Air/Vacuum Leaks
• Fuel Pressure
• Input Sensor that influence
air/fuel mixture
• Engine Mechanical
2
2.5
3
3.5
t Rest Lean1
4
4.5
Time
5
5.5
6
6.5
7
7.5
8
8.5
9
t Rest Lean2
13550011.eps
NOTE: A MIXTURE RELATED FAULT CODE SHOULD BE INVESTIGATED FIRST AND DOES NOT
ALWAYS INDICATE A DEFECTIVE OXYGEN SENSOR!
76
ST055 M1.7.2 Emissions Management
Tools and Equipment
The DIS/Modic as well as a reputable hand held
multimeter can be used when testing inputs/
components.
It is best to make the checks at the ECM connection, this method includes testing the wiring
harness.
The correct Universal Adapter for the M1.7.2
application should be used (#88 88 6 614 410).
This will ensure the pin connectors and the harness will not be damaged.
The interior of this Universal Adapter is shielded,
therefore it is vital that the ground cable is connected to the vehicle chassis whenever the
adapter is used.
07550003.eps
88 Pin
Adapter
The adapter uses a Printed Circuit board inside
keeping the capacitive and inductive load to a
minimum.
When installing the Universal Adapter to the
ECM (located below the windshield on the passenger side of the engine compartment), make
sure the ignition is switched off.
12550005.eps
Troubleshooting the closed-loop oxygen sensor
control should be performed using Special Tool
# 90 88 6 117 450 (operational instruction book
included).
Refer to Repair Information 13 00 060 for
detailed information on checking exhaust contents.
04550001.bmp
77
ST055 M1.7.2 Emissions Management
Performance Controls
12550017.eps
Engine Speed Signal (TD): is produced by the
ECM as an output function. The TD signal is a
processed square wave signal that indicates
engine rpm. The signal is made available to
other control modules including the Instrument
Cluster, EWS and the 20 pin Diagnostic Socket.
74
The TD output is a square wave modulated signal. The frequency of the signal is directly proportional to RPM. The receiving control module
detects RPM by the number of pulses.
3
Load Signal (Ti): is produced by the ECM as
an output function that represents the actual
amount of fuel injected. It is made available to
other control modules as an input for operation.
These control modules include:
2
4
5
1/ min
x 1000
6
1
50
30 20
16
7
12
• OBC=Fuel consumption for MPG and Range.
• Instrument Cluster = MPG Gauge
• EGS = Load signal for shift points
(If Equipped)
17
The Ti output is a processed square wave signal. The frequency of the signal is proportional to
engine RPM. The pulse width and duty cycle will
vary to reflect the injection quantity.
12550019.eps
78
ST055 M1.7.2 Performance Controls
Engine Speed (TR) for EGS: is an additional
variation of the engine speed signal. The “TR”
signal is produced ECM as an additional output
function. Like TD, “TR” is a processed signal
that indicates engine rpm for the EGS (if equipped) to determine shift points.
TR Signal
1
The TR signal is a pulse wave signal. The frequency of the signal directly proportional to
RPM. The signal is overlapped on the fuel pump
relay control signal from the ECM.
62550001.eps
Throttle Position (DKV) for EGS: is the output signal to the EGS Control Module (if equipped). The DKV signal is a pulse width modulated signal directly proportional to the linear throttle position sensor input signal.
11
This output signal is used by the EGS Control
Module for determining shift points.
EGS
DKV Signal
62550002.eps
The EGS releases the ground so the ECM will
resume ignition timing advance at the completion of the “shift”.
ECM
EGS Ignition Timing Intervention Signal:
The ECM receives an input signal from the EGS
Control Module (if equipped) that will retard the
ignition timing. This is a momentary ground signal from the EGS during a gear change to
reduce engine torque for smoother shifts.
10
EGS
62550003.eps
79
ST055 M1.7.2 Performance Controls
A/C Compressor Control: is an output of the ECM. The ECM controls the A/C
Compressor Relay based on signals from the IHKA/IHKR Control Modules.
When the driver selects the “snow flake” button, the IHKA/IHKR Control Module signals
the ECM (AC) which “arms” it for compressor activation.
The ECM prepares for the additional load of the compressor by modifying the ignition timing and stabilizing idle speed.
When A/C compressor activation is required the IHKA/IHKS signals the ECM through the
high/low refrigerant pressure switches (KO). The ECM will provide a ground circuit for the
A/C Compressor Relay.
The A/C Compressor Relay is deactivated during wide open throttle acceleration at low
speeds to allow the engine to quickly achieve maximum power.
62550004.eps
80
ST055 M1.7.2 Performance Controls
Driveaway Protection System Interface EWS I (1-94 thru 12-94 production): was
added to all vehicles in January 1994. It is controlled by the Central Locking System of ZKE
and by the On-Board Computer code function (if equipped).
The Starter Immobilization Relay is activated when:
• The vehicle is locked from the outside (Central Locking - GM output to Relay).
• The On-Board Code function is set.
An activated relay performs two functions to deter vehicle theft:
• Ignition and Injection functions of DME are disabled (switched high output signal.)
• The KL 50 start signal circuit is opened to prevent starter operation.
* Conventional troubleshooting using the ETM.
ECM
ECM
62550005.eps
81
ST055 M1.7.2 Performance Controls
Driveaway Protection System Interface EWS II (from 1-95 production): and ECM
Control Modules are synchronized through an individual serial number (ISN). The ISN is
a unique code number that is permanently assigned to the ECM and also stored in the
EWS II Control Module. The ISN must match every time the ignition is switched “ON”,
before the ECM drive away protection feature will be cancelled.
• Engine Control Modules designed to operate with the EWS II system will not interchange
with ECMs from previous models.
• The ISN replaces the BC Code input to the ECM.
• The ISN is unique to each ECM and cannot be changed or overwritten. The ISN is transferred /
stored in the EWS II Control Module using the DIS/MoDIC (including diagnosis).
• Everything the ignition is switched “ON” the ISN number is sent from the EWS Control Module
to the ECM, as a digital coded signal. The numbers must match before the ECM will release
the driveaway protection.
• The ISN is continuously sent to the ECM as long as the ignition is switched on (KL15).
• The ECM will disregard the loss of the ISN after the engine is running.
ECM
4X
62550006.eps
82
ST055 M1.7.2 Performance Controls
Variant Coding
The ECM used in the M1.7.2 system is a codeable module that requires Variant Coding if
it is replaced. The control module is programmed with “resident data” stored in the EPROM
and Variant Coding simply means that one of the “data sets” will be activated for the
engine/vehicle.
DME (ECM) Variant Coding is performed with the DIS/MoDIC using the latest software:
• DME Varient Coding uses a 4
Digit code to determine which
of the internal maps (data sets)
to utilize.
• The 4 digit code describes which
maps to use.
Modic III
Resident
Data
Coding ID
Segment
• The proper variant code can be
found on the cover of the old
ECM or Modic variant coding
software.
• The actual program software
can be found for DME variant
coding can be found only in
DME Programing software.
Unique Code
• A codeable DME can only be
coded 8 times.
(Uncoded Control)
Module
12550003.eps
Please refer to the following Service Information Bulletins for updated information on the
ECM regarding coding:
• SI #09 Group for the latest on Programing/Coding Explanation
• SI #12 14 97 M42 Fault Code 200/333
• SI #12 15 97 M42 Acceleration Jot in 2nd and 3rd Gear
• SI #12 09 95 M42 ECM (DME) 1.7.2 Fault Code 41
83
ST055 M1.7.2 Performance Controls
Workshop Hints
The following signals are “manufactured” by the ECM for
other control modules and are not the “raw” inputs to the
ECM.
These signals should be tested if another Control Module,
gauge or function is inoperative due to a lack of the signal(s).
With the 88 Pin adapter and the DIS Oscil- loscope (Preset
Measurements) the following signals can be observed with
the ECM installed and engine running:
25
1.
50
20
40
15
30
10
20
5
10
07550007.eps0
0
2.
25
50
20
40
15
30
10
20
5
10
1. TD = Engine RPM
2. Ti = Fuel Injection
3. TR = Engine RPM (for EGS if equipped)
4. DKV = Throttle Postion (for EGS if equipped)
0
0
07550005.eps
3.
The waveform on the scope should be even, continuous,
without interference and of sufficient heigth (indicates signal
strength). Examples of “good” patterns are shown to the right.
The test should be performed at the ECM and at the output
Controle Module/component.
25
50
20
40
15
30
10
20
5
10
0
0
07550004.eps
4.
25
50
20
40
15
30
10
20
5
10
0
84
ST055 M1.7.2 Performance Controls
0
07550008.eps
Tools and Equipment
The DIS/Modic as well as a reputable hand held
multimeter can be used when testing inputs/
components.
It is best to make the checks at the ECM connection, this method includes testing the wiring
harness.
The correct Universal Adapter for the M1.7.2
application should be used (#88 88 6 614 410).
This will ensure the pin connectors and the harness will not be damaged.
07410000.eps
The interior of this Universal Adapter is shielded,
therefore it is vital that the ground cable is connected to the vehicle chassis whenever the
adapter is used.
88 Pin
Adapter
The adapter uses a Printed Circuit board inside
keeping the capacitive and inductive load to a
minimum.
12550005.eps
When installing the Universal Adapter to the
ECM (located below the windshield on the passenger side of the engine compartment), make
sure the ignition is switched off.
85
ST055 M1.7.2 Performance Controls
Review Questions
1. Describe the Power Supply for the Fuel Injectors:________________________________
__________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
2. Name the Components of the Fuel Supply System:
________________
_______________
_______________
________________
_______________
_______________
3. List the inputs required for igniton operation:
________________
_______________
________________
_______________
_______________
_______________
____________
4. Describe the Knock Sensor Function:__________________________________________
__________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
5. Name two types of Emissions the ECM controls:______________
______________
6. List two reasons for the “CHECK ENGINE” Light to illuminate:
__________________________________________________________________________
__________________________________________________________________________
7. List four different tests that can be performed on the fuel injectors:
__________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
8. Describe Semi-Sequential Injection: ___________________________________________
__________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
9. EWS (I or II) affects what ECM output functions to deter vehicle theft?
__________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
86
ST055 M1.7.2 Performance Controls